Norepinephrine Dosing in Septic Shock
Start norepinephrine at 0.5-0.7 mg/hr (approximately 8-12 mcg/min) and titrate to maintain a mean arterial pressure (MAP) of 65 mmHg, with typical maintenance doses ranging from 0.12-0.24 mg/hr (2-4 mcg/min) and maximum doses potentially reaching 4 mg/hr (68 mg/day) in refractory cases.
Initial Dosing Strategy
The FDA-approved labeling provides clear guidance 1:
- Standard concentration: 4 mg norepinephrine base in 1000 mL D5W (4 mcg/mL)
- Starting dose: 2-3 mL/min of this solution = 8-12 mcg/min = 0.48-0.72 mg/hr
- Maintenance range: 0.5-1 mL/min = 2-4 mcg/min = 0.12-0.24 mg/hr
Titration Approach
Norepinephrine is the first-choice vasopressor per Surviving Sepsis Campaign guidelines 2. The titration strategy should follow this algorithm:
Step 1: Ensure adequate fluid resuscitation first - Blood volume depletion must be corrected before or concurrent with vasopressor initiation 1
Step 2: Target MAP of 65 mmHg - This is the initial hemodynamic goal 2, though individualization based on prior hypertension may be warranted (target no higher than 40 mmHg below baseline systolic pressure) 1
Step 3: Escalate norepinephrine as needed - Titrate based on hemodynamic response, not arbitrary dose limits 1
Dose Ranges and Clinical Implications
Moderate Doses (0.12-0.6 mg/hr)
Most patients respond within this range. Research shows norepinephrine at 0.3-0.6 mcg/kg/min (approximately 0.36-0.72 mg/hr for a 70kg patient) improves left ventricular systolic function and ventriculoarterial coupling 3.
High Doses (>0.6 mg/hr)
A maximum dose within 24 hours of ≥0.6 mcg/kg/min (approximately 2.5 mg/hr for 70kg patient) is associated with increased 7-day mortality and may indicate refractory septic shock 4. This threshold should prompt consideration of adjunctive vasopressors.
Very High Doses (>4 mg/hr)
Doses exceeding 4 mcg/kg/min (approximately 17 mg/hr for 70kg patient) are occasionally necessary. One study documented safe use up to 68 mg/day (2.8 mg/hr) with 33% survival in otherwise refractory shock 5. However, occult hypovolemia must be aggressively excluded at these doses 1.
When to Add Second-Line Vasopressors
Add vasopressin 0.03 units/min when norepinephrine reaches 0.3-0.6 mg/hr (moderate doses) rather than continuing to escalate norepinephrine alone 2, 6. This strategy:
- Reduces catecholamine exposure and associated complications
- May improve renal perfusion 7
- Decreases risk of atrial fibrillation 8
Consider epinephrine as an alternative second agent if additional inotropy is needed 2.
Critical Pitfalls to Avoid
Delaying initiation while pursuing fluid resuscitation: Norepinephrine can be started concurrently with volume replacement when MAP is critically low 1
Assuming high doses indicate futility: Doses up to 4 mg/hr may be appropriate if hypovolemia is excluded and tissue perfusion improves 5
Using saline as diluent: Must use dextrose-containing solutions to prevent oxidation and loss of potency 1
Peripheral administration concerns: While central access is preferred, early peripheral initiation is increasingly recognized as acceptable to avoid delays 8
Fixed MAP targets: While 65 mmHg is the guideline target 2, emerging evidence suggests perfusion-guided monitoring (e.g., capillary refill time, lactate clearance) may better optimize dosing than rigid MAP goals 9, 8
Practical Conversion
For quick reference:
- 1 mg/hr = 16.7 mcg/min
- 0.1 mcg/kg/min for 70kg patient = 0.42 mg/hr
- Standard 4 mcg/mL concentration at 15 mL/hr = 1 mg/hr